Act III – The Shadow of Numidium

Act III is the climax of the conflict on Nirn. Armed with acquired knowledge, the PCs seek to counter the Thalmor's plan – which turns out to be even more terrible than imagined. The Aldmeri Dominion is preparing not only to travel into the Void but to cause a cataclysm capable of reshaping the world (their ultimate goal, according to some fan theories, being to weaken the reality of Mundus to regain their lost divine immortality). This potentially leads to the fulfillment of the Landfall prophecy: the fall of Nirn.

Aware that they cannot act alone against an entire empire, the PCs will seek support. They can return to the Empire in Cyrodiil: perhaps a Legate or a member of the Elder Council summons them, having heard of their discoveries. Important lore figures can appear as allies: for example, the reigning Empress (or Emperor) if a new ruler has succeeded Titus Mede II, or the heir of a Great House of Morrowind curious about Dwemer technologies. The Mages Guild (or the Synod/Order of Whispers depending on the era) can also be involved, sending an Archmage to cooperate with them. This more narrative phase allows for forging alliances: the PCs could convince a local lord to discreetly divert resources to build the aethernautic vessel described in their plans (a difficult Speechcraft check with bonuses if good deeds were accomplished in Act II).

As preparations are made, war openly breaks out between the Empire and the Aldmeri Dominion. The Thalmor, having advanced their pawns, launch an offensive on Cyrodiil and High Rock. The PCs may be caught in the turmoil of a major pitched battle – for example, the Battle of Anvil (southern Cyrodiil) or a siege of a strategic port. This is an opportunity for large-scale combat scenes: they can lead a squad (Command skill possible if one of them has the soul of a leader), or accomplish an infiltration mission during the battle (e.g., penetrate behind enemy lines to sabotage ballistas, which requires Stealth and Lockpicking under pressure). This martial aspect gives an epic scope to the campaign and recalls the underlying conflicts of the universe.

During these clashes, the stars align for the worst. The Thalmor succeed in their ritual or activate their device: Numidium – the immense Dwemer golem capable of bending reality, once used by Tiber Septim – makes its thunderous return. Whether it is the original Numidium reconstituted or a derivative creation, its power is cataclysmic. The besieged city trembles as this brass titan materializes in the heart of the battle. It obliterates entire regiments with a devastating beam. It is absolute horror: no mortal can contend with such a force. Players will understand that they must adapt their approach – direct confrontation is impossible, another way must be found.

Facing the impending apocalypse, the Imperial entourage decides to activate the last-ditch plan, with the help of the PCs. Thanks to the Dwemer artifact/plans recovered in Act II, an aethernautic vessel could be hastily built or repaired – possibly a Dwemer airship converted for space travel. This vessel, named for example the Hope of Cyrodiil, is powered by the aetherium fragment and the combined magic of several mages. Its objective: to take a commando (the PCs) beyond Nirn, either to seek help or to strike the enemy from an unexpected angle. For example, one strategy could be to travel to the Moon Secunda or Masser where an ancient planetary pylon capable of deactivating Numidium remotely is located (here we integrate a lore element – the moons being linked to the divinity of Lorkhan, their control could affect the creature built with the heart of Lorkhan). Alternatively, the idea might be to directly penetrate the Void of Oblivion to reach Aetherius and beg for the intervention of the Divines or activate an Aedric artifact.

The end of Act III sees the PCs embark on the vessel and take off from Tamriel. The scene is exceptional: they pierce the stormy sky while, beneath their feet, the Empire and the Dominion fight their last battle. This is a first for mortals in millennia – space travel becomes concrete. However, reaching Nirn's orbit is not without risks: the journey crosses the Void, that is, the realm of Oblivion itself. One can describe a surreal passage where the stars are breaches of Aetherius in the darkness of Oblivion, where strange winged creatures (Daedric mantises or star-vampires) attack the astral ship. The PCs must defend the vessel in the void (Destruction spells cast into the icy void, combat on the ship's deck under a starry sky – a unique opportunity to blend magic and combat in an unprecedented setting). Possible effects on the mind may afflict them (one who stares too long into the Void without protection feels cosmic dread – a small improvised Willpower/Intelligence check can be added, or use Perception to navigate this non-space). By successfully overcoming these perils, the crew finally reaches its goal: the celestial body targeted (for example, the moon Masser). Cliffhanger: Act IV will take place on an extraterrestrial soil.